Continuous spinning and drawing of polycaproamide yarn



Jan. 13, 1970 J. l. BRUTON ETAI. 3,489,832

CONTINUOUS SPINNING AND DRAWING OF POLYCAPROAMIDE YARN Filed April 2e, 1967 SPIN BLOCK A Q PROBE FOR MEASURING I Ik TEMPERATURE oF YARN 1 .I:| I2 (NOT OVER 55C) ORIP cATcI-IER//T HEATER II; SECOND 26 THIRD LJIJI GODET GODET FINISH ROLL ROLL ROLL WINDER NVENTORS: JAMES I. Bau-raw um@ n Susan AT TGRN EY vUnited States Patent U.S. Cl. 264-237 9 Claims ABSTRACT OF THE DISCLOSURE The process allows spinning polycaproamide multifilament yarn at high rates of 25 lbs. per hour and above into undrawn filaments of 401-100 denier per filament, delivering these filaments from the quench zone at rates of at least 1000 ft. per minute, and continuously drawing the resulting filaments at draw ratio of at least 3.5: 1. An intensive air quench is provided, such that the temperature of the filaments leaving the quench zone is not above 55 C. In particular the quenching is by use of entering air at temperature not above 35 C. and at volumetric ow rate of at least 100 cu. ft. per lb. of extruded filaments, which quench air is split to exhaust a minor portion upward and exhaust the major portion from a zone below one air inlet and above a second air inlet.

BACKGROUND OF THE INVENTION This invention relates to melt spinning of polycaproamide filament, especially polycaproamide multifilament yarn, followed immediately by drawing the cooled filament without an intermediate step of winding up the undrawn filament.

It is conventional in melt spinning polycarbonamides to spin the melt as filaments into a quenching zone such as a vertical tower wherein quenching air cools the molten filaments, and to wind up the resulting filaments at the exit from the quenching zone under low tension. A lubricating composition in the form of an aqueous emulsion is commonly applied just before the filaments are wound up, to facilitate further processing. Thereafter the filaments which have been Wound are kept in a constant humidity atmosphere (lagged) and thereafter they are stretched to impart molecular orientation and to increase the tenacity (measured by ultimate tensile strength). Operations of this sort are disclosed for example in U.S. Patents 2,289,860 of July 14, 1942 to Babcock; 2,918,347 of Dec. 22, 1959 to Notarbartolo et al.; and 3,113,369 of Dec. 10, 1963 to Barrett et al.

It would obviously be of advantage to eliminate the step of winding up the undrawn yarn at the exit from the quenching zone; the step of lagging this yarn; and the step of unwinding this yarn for purposes of drawing it` Processes for continuous spinning and drawing, without these intermediate steps, have been proposed for application to poly(hexamethylene adipamide) i.e. nylon 66 spinning e.g. in U.S, Patent 3,090,997 of May 28, 1963 to Tin-Yam Au; and U.S. Patent 3,093,881 of June 18, 1963 to Zimmerman. It will be noted that in the Zimmerman patent, the only example discussing polycaproamide discloses packaging the undrawn yarn and drawing it in a separate step, rather than continuous spinning and drawing-Example XIV.

The continuous spinning and drawing of polycaproamide is found to present special problems of obtaining good performance, i.e. freedom from breakage of filaments causing wraps around the draw rolls, while still obtaining tenacities (UTS) of at least 4 grams per denier at break, (based on original yarn dimensions). These 3,489,832 Patented Jan. 13, 1970 special problems may arise from the known fact that polycaproamide is capable of existing in 3 different crystal forms which tend to convert from one into the other (see Roldan & Kaufman, Journal of Polymer Schience, Part B vol. 1 of 196-3 (Polymer Ietters) pages 603-608).

One procedure which has been proposed to meet the problems of continuous spinning and drawing of polycaproamide is.the draw the filaments while hot in the spinning tower instead of drawing cool yarn (U.S. Patent 3,053,611 of Sept. 11, 1962 to Griehl). This procedure, however, creates its own problems in that it is very demanding on apparatus to maintain the high uniformity of tensions, speeds, cooling rates, etc. which are required for good uniformity of the resulting filaments. Such demands are especially difficult to achieve when the yarn consists of a large number of individual filaments such as 30 filaments or more.

SUMMARY OF THE INVENTION It has now been found that a poly-E-caproamide multifilament yarn, including such yarn of high denier per filament, e.g. 40-100 denier per filament (undrawn), can be melt spun continuously at high production rates such as 25 lbs. per hour and preferably 1000 feet per minute delivery speed from the cooling zone; and this yarn can be continuously drawn without an intermediate step of winding up, at draw ratios of at least 3.5: 1. These results are achieved, in accordance with this invention, by ernploying intensive quenching of the melt spun filaments before drawing same; whereby the temperature of these filaments is reduced to not over 55 C. as measured by a thermistor in contact with the filaments, prior to the drawing of the filaments. The birefringence of these undrawn filaments is found to be not above 0.005. More particularly in the present process, a relatively large number of heavy filaments are extruded simultaneously into a single quench zone, viz., at least about 60 filaments each having undrawn denier of about 40-100; and the temperature reduction of these extruded filaments is accomplished by contacting the filaments with air entering the stack at a volumetric flow rate of about 1GO-300 cubic feet of air (measured at standard temperature and pressure) per pound of entering filaments, the air being at inlet temperature preferably not above 35 C. Especially effective is a split fiow of air in the cooling zone. A minor proportion, especially 1%-25% of the total inlet air flows upward and is exhausted in the vicinity of the spinneret; and the major proportion is further split by being admitted at two air inlet zones, one of which is at least 5 feet above the principal exhaust zone and the other is at least 5 feet below that exhaust zone.

PREFERRED EMBODIMENTS The accompanying drawing is a diagrammatic flow chart illustrating certain features of the invention. Yarn 1 is shown being extruded as filaments into quench stack 2 from spin block 4. Near the top of the quench stack is inlet air plenum 6 and above it is monomer exhaust plenum 8. Air is shown entering the inlet plenum 6, a minor proportion of which flows upwardly and out monomer exhaust plenum 6, while the major proportion liows downward cocurrent with the descending filaments and out via main exhaust plenum 10. A further quantity of air enters at the base of the tower 12 where the filaments emerge, and fiows countercurrent to the descending filaments to be exhausted from the main exhaust plenum 10. A plenum near the base of the tower at least five feet below the main exhaust plenum 10 can be provided for this last iiow of air instead of using the egress opening 12 at the bottom of the stack, if desired; such operation allows controlling the temperature and humidity of the incoming air independently of the room air.

The emerging filaments pass from the egress opening 12 to a conventional drip catcher 14 and then contact a conventional finish roll 16. Then the yarn passes around the first godet roll 18 and is drawn between this and the second godet roll 20. A third godet roll 22 can be provided if a yarn-treating zone such as an annealing zone is desired. The yarn is taken up upon a package by winding machine 24, either direct from the second godet or after passing through a zone such as the annealing zone provided by heater 26 and third godet 22.

Yarn temperatures at a point just below the egress opening 12 can be measured by contacting the yarn with a thermistor probe 30. In operations in accordance with this invention, such temperatures are found to be 55 C. or less.

The legends on the flow chart show illustrating conditions as used in the herein examples.

In the examples which follows, summarized in the table below, preferred embodiments of the invention illustrative of the best mode contemplated by the inventors viz. a commercially available glass-encapsulated temperature-sensitive semiconductor made from sintered metal oxides, having a resistance of about 100,000 ohms at 20 C. and having a negative temperature coefiicient of resistance.

The ya-rn as it left the quench stack contacted a finish roll which applied a non-aqueous finish of the general type disclosed in copending application of Stanley R. Ross, Ser. No. 610,000, filed Ian. 18, 1967. The yarn then passed in three wraps around a godet (a roll and separator) then in three wraps over a second godet running at a higher peripheral speed than the first godet whereby to draw the yarn, then to a conventional parallel winding machine which wound the yarn under light controlled tension. The draw ratios cited below are the ratios of peripheral speed between the second and the first godet rolls.

The conditions used in the exemplary runs and comparison runs, and the physical properties of the resulting drawn yarn (measured upon the Instron tensile tester) are shown in the accompanying table. Except as otherwise shown in the table, all conditions were kept the same in all runs of the table.

TABLE [THROUGHPUT OF POLYMER 40 LB./HR.]

Physicals Quench air, cfm. Ultimate Ultimate inlet Exit; Undrawn elongation tensile exhaust yarn yarn bire- Maximum (UE), strength at plenum temp., C. fringence draw ratio percent (UTS), g./d.

C omparisons:

(A) Al/20 82 0. 030 (B) 60/40 75 0. 025 (C) U/80 65 0. O15 3. 05 70. 1 4. 4 This invention.'

Ex. l l0/8() 52 0. O04 3. 85 0 4. 8

(Throughput of polymer=30lb./h1.) Ex. 2 40/80 40 0. 003 4. 00 4 4. 6

for carrying out the invention are set forth; and comparison examples illustrating the criticality of conditions and the unexpected advantages of the invention are also set forth. The invention is not to be understood, however, as being limited to all details of the examples.

The spinning apparatus used in all of the runs described below employed the usual sand-filled spin pack for melt spinning yarn, provided with a spinneret containing 136 holes each of 0.018 inch diameter. Below the spinneret was a vertical stack provided with an air inlet plenum located about l foot below the spinneret, a monomer exhaust plenum above said inlet plenum and a main exhaust plenum about l2 feet below the inlet plenum and about 8 feet from the base; the whole stack was about 22 feet long. The Vgeneral structure of the stack was as illustrated in Dulin U.S. Patent 3,257,487 of July 2l, 1966.

The temperature of the inlet air was 28 C. and its relative humidity at that temperature was 65%. This air was drawn into the upper part of the stack through the inlet plenum at a rate of 40 c.f.m. i.e, cubic feet per minute at standard temperature and pressure (240 cu.- ft. per hr. S.T.P.) in the runs in accordance with the invention; whereas in the comparison runs the air flow was varied as indicated in the table below. In the examples of the invention, the air was exhausted from the stack through the main exhaust plenum at a rate of 80 c.f.m.,' and in all runs about -20 c.f.m. of air and monomer vapors was removed via the monomer exhaust plenum at the top of the tower. Any difference between the inlet and exhaust flows was made up by air entering or exhausting at the base where the descending filaments emerged from the stack, below the main exhaust plenum.

The temperature of the melt prior to extrusion through the spinneret was about 257 C., and the rate of extrusion of melt into filaments was either 30 or 40 lbs. per hour as indicated in the tables.

The yarn temperature at the exit from the stack was measured by contacting the yarn with a thermistor probe,

The yarn of Example l, without annealing, had shrinkage in boiling water of about 20%. This value could be reduced materially by heat annealing, the reduction being accompanied by an increase in UE with little or no change in UTS.

ln the above tables it will be observed that, when an exit yarn temperature of not above 55 C. is achieved, it is possible to draw this yarn at a draw ratio of at least 3.5, and the ultimate elongation (UE) of the resulting yarn is not above 60%.

Especially when processing filaments of heavy denier, such as 40-100 denier per undrawn filament, use of a draw ratio of' at least 3.5 is important. Yarns drawn at a lower ratio generally have relatively low ultimate tensile strength (UTS) and relatively high ultimate elongation. Moreover these continuously spun and drawn yarns show considerable creep, i.e. retraction upon standing. Under excessive creep the shape of a wound package of the yarn becomes distorted as the yarn retracts; and the turns of yarn may entangle so that the package will fail to unwind. When a large package is wound firmly enough to hold on the core, the package core may even be crushed by the retractive force exerted by creep The yarn produced in accordance with this invention can be brought to a satisfactory level of dimensional stability so that it can be packaged in acceptable large packages of 2 pounds and more. Such dimensional stability can be achieved by an annealing operation or by drawing the yarn at a ratio lower than the maximum operable ratio (being the highest ratio which is compatible with drawing performance showing no more than 0.06 sum total of broken filaments wrapping on the rolls (wraps) and breaks of the yarn in the draw zone (breaks) per pound of yarn packaged). Annealing can be effected by passing the drawn yarn through a heated zone while holding the yarn at constant length or allowing limited contraction. For instance, the yarn can be annealed generally as in U.S. Patent 2,199,- 411 of May 7, 1940 to Lewis or as in U.S. 'Patent 2,803,108

of Aug. 20, 1957 to Stoddard et al. or as in U.S. Patent 2,859,472 of Nov. 11, 1958 to Wincklhofer. If desired, the heat for annealing can be supplied directly to the second godet roll rather than using a heating shoe as in the Wincklhofer patent, e.g. as in U.S. Patent 2,611,923 of Sept. 30, 1952 to Hume.

The higher shrinkage characteristic of yarn produced in accordance with this invention can be utilized for certain purposes as known in the art. For instance, such yarn of high shrinkage characteristics can be plied by twisting, or entangled or otherwise combined with a yarn having lower shrinkage; and upon being subjected to shrink conditions, such as dry heat, hot aqueous bath, etc. the composite yarn will pucker and crimp as a result of difference in shrinkage between the components. This high shrinkage yarn is also readily crimpable by dilferential heating methods such as hot edge crimping as in U.S. Patent 2,875,502 of Mar. 3, 1959 to Matthews et al.; U.S. Patent 2,919,534 of Jan. 5, 1960 to Bolinger et al.; and hot pin crimping as in U.S. Patent 2,974,391 of Mar. 14, 1961 to Speakman et al.

Although the above test runs were made with polymer consisting essentially of polycapro'amide, it is to be understood that polymers wherein polycaproamide is the major ingredient are also similarly processable. For example, polymer blends of a compatible or incompatible resin or polymer dispersed in polycaprolactam can be processed in generally the same manner as in the above examples to give generally the same or similar results. Exemplary of such blends are polycaproamide in major proportion together with a minor proportion of another polyamide such as nylon 66 or nylon 6-10 or polyamide from a dicarboxylic acid and a ring-containing diamine, e.g. aromatic or cycloaliphatic ring; or polycaproamide having dispersed therein a polyester, such as polyethylene terephthalate; or a dispersed polymerized olen or vinyl compound such as polyethylene, polypropylene, polystyrene, polyvinylchloride; or dispersed acrylic polymer such as polyacrylonitrile or polymethyl methacrylate; or dispersed copolymers or mixtures of the foregoing resins and polymers.

Other modifying agents of polycaproamide as well as the foregoing resins or polymers can also be present such as pigments, stabilizers, lubricants, etc., e.g., as disclosed in U.S. Patent 2,705,227 of Mar. 29, 1955, to Stamatoff; U.S. Patent 3,242,134 of Mar. 22, 1966, to Papero; etc.

The invention claimed is:

1. A process for continuously producing a plurality of laments from a melt containing poly-e-caproamide as the major component, which comprises:

(a) extruding the melt through a spinnerette into a quench chamber at a rate of at least 25 pounds per hour to form a plurality of iilaments,

(b) contacting the filaments with a volumetric rate of 100 to 300 cubic feet of air (S.T.P.) per pound of entering filaments in the quench chamber, said air being introduced simultaneously at a point intermediate said chamber and at a point in the vicinity of the end thereof farthest from the spinnerette,

(c) exhausting the air from said chamber simultaneously at the point of extrusion and a point intermediate said inlets whereby said air in said chamber contacts said filaments countercurrent, cocurrent 'and countercurrent in progressive order of their movement from said extrusion point, and

(d) withdrawing the filaments from the quench charnber.

2. A process as described in claim 1 wherein the filaments are cooled to below 55 C. as measured by a thermistor in contact with the filaments as the exit of said chamber.

3. A process as described in claim 2 further characterized by simultaneously drawing the larnents at least 3.5 times their length upon departure from the quench chamber prior to take-up.

4. A process as described in claim 3 wherein the lilaments are withdrawn from the quenching chamber at a delivery speed greater than 1000 feet per minute.

5. A process as described in cl-aim 4 wherein the air exhausted between said inlets departs said chamber at a point at least 5 feet distance from the said inlets.

y6. A process as described in claim 5 wherein 1 to 25 percent of the air introduced intermediate said chamber is exhausted through a monomer exhaust outlet located adjacent to the point of extrusion.

7. A process as described in claim 6 wherein a major portion of the air exhausted at said intermedi-ate exhaust point is introduced through the air inlet at said end.

8. A process as described in claim 1 wherein the lilaments have an undrawn denier of about 40-100 and a birefringence not 'above 0.005.

9. A process as described in claim 1 wherein the air before entering the quench chamber is not about 35 C References Cited UNITED STATES PATENTS 2,273,105 2/ 1942 Heckert.

2,957,747 10/1960 Bowling 264-168 2,991,147 7/ 1961 Thomas.

3,118,012 1/1964 Kalray.

3,271,943 9/1966 Williams 264-168 X 3,389,429 6/ 1968 Montgomery.

3,257,487 6/1966 Dulin.

JULIUS FROME, Primary Examiner J. H. WOO, Assistant Examiner U.S. Cl. X.R. 264-176, 210, 234 

